计算下各题,能用简便方法计算的要用简便方法计算.
12×=________;
47×=________;
÷23+×=________;
0.25×13.8+6.2÷4=________;
6.48÷[(3.3-2.7)×0.9]=________;
=________.
网友回答
4 8 5 12
解析分析:(1)运用乘法分配律简算;
(2)先把47分解成(48-1),再运用乘法分配律简算;
(3)(4)先把除法变成乘法,再运用乘法分配律简算;
(5)先算小括号里面的减法,再算中括号里面的乘法,最后算括号外的除法;
(6)先算小括号里面的除法,再算小括号里面的加法,最后算括号外的乘法.
解答:(1)12×,
=12×+12×-12×,
=3+2-1,
=4;(2)47×,
=(48-1)×,
=48×-1×,
=9-,
=8;(3)÷23+×,
=×+×,
=(+)×,
=1×,
=;(4)0.25×13.8+6.2÷4,
=0.25×13.8+6.2×0.25,
=0.25×(13.8+6.2),
=0.25×20,
=5;(5)6.48÷[(3.3-2.7)×0.9],
=6.48÷[0.6×0.9],
=6.48÷0.54,
=12;(6),
=×(+),
=×,
=.
点评:此题是考查四则混合运算,要仔细观察算式的特点,灵活运用一些定律进行简便计算.